Pseudomonas aeruginosa Infections
Pseudomonas aeruginosa are Gram-negative, flagellated rod bacteria that continue to be a significant pathogen in nosocomial infections resulting from surgery, prosthesis implantation and respiratory tract procedures. Pseudomonas aeruginosa also is an opportunistic pathogen in the etiology of cancer, cystic fibrosis, diabetes, heart disease, otitis externa (swimmer's ear), osteomyelitis, corneal ulcers, folliculitis, mastitis, pneumonia, meningitis, urinary tract infections, endocarditis, peritonitis and other diseases found in geriatric or immunocompromised patients.
Surgical patients are often at increased risk of Pseudomonas aeruginosa infection by virtue of their illness (e.g., trauma, burns, inhalation injury and cancer) or treatment (e.g., disruption of natural epithelial barriers by incision or percutaneous catheterization, endotracheal intubation, cardiac and thoracic surgery, neurosurgery, and gastrointestinal surgery). Disruption of natural intestinal flora by antibiotic treatments or prophylaxis, therapeutic immunosuppression of solid organ transplant recipients, or environmental exposure to Pseudomonas aeruginosa can place patients at increased risk. Moreover, multi-drug-resistant strains can cause significant infections in inpatient units as well as nursing homes.
Surgical patients are affected by nosocomial pneumonia, often caused by Pseudomonas aeruginosa. Onset occurs after the first 72 hours of hospitalization and is characterized by fever, purulent sputum, leukocytosis and a new or changed lung infiltrate revealed by chest radiography. The oropharynx is colonized rapidly, which may spread into the lower respiratory tract. Incidence of nosocomial infection in surgical patients overall is approximately 5% to 8%, and is probably higher in all critically ill patients. The incidence of pneumonia reported from surgical intensive care units (ICUs) is 15% to 20%, and occasionally higher. See Barie et al. Am. J. Surgery 179:2 S-7S (2000).
Cystic fibrosis (CF) patients suffer chronic colonization with a narrow but evolving spectrum of bacterial pathogens Pseudomonas aeruginosa remains the major CF pathogen with a worldwide prevalence of up to 80% to 90% in CF adults. Such infections lead to intermittent episodes of debilitating inflammatory exacerbations and progressive lung damage. Emerging pathogens also tend to be resistant to multiple antibiotic regimens, thus infection control plays a critical role in the quality of life and life expectancy of CF patients.
The onset of chronic colonization is associated with acceleration of forced expiratory volume (FEV). The original colonizing strain transforms into a mucoid colonial form which is due to copious production of a highly viscid exopolysaccharide known as alginate. The colonizing strain becomes significantly more mucinophilic and chemotactic and is associated with impaired mucociliary clearance. See Govan J. Royal Soc. Med. 93 Supp. 38:40-45 (2000). Moreover, the Pseudomonas aeruginosa isolated from lungs of CF patients show changes in the LPS fatty acid acylation pattern and enhanced resistance to the bactericidal activity of some cationic antimicrobial peptides (CAMPs).
Alterations in Pseudomonas aeruginosa LPS lipid A were found in CF isolates that increased both bacterial resistance to antimicrobial peptides and the ability of LPS to elicit inflammatory mediators. CF patients have very high antibody titers to Pseudomonas aeruginosa LPS in both serum and sputum, which might neutralize its biological activities in vivo (e.g. proinflammatory mediator release). See Pier Trends Micriobiol. 8:247-251 (2000).
The leading cause of morbidity and mortality in severe burn wounds patients is infection with Pseudomonas aeruginosa, See Lee et al. Vaccine 18:1952-1961 (2000). Burn wounds are highly exudative, creating a moist, nutrient-rich environment for bacterial colonization. Burn wounds are largely inaccessible to the patient's immune responses and vascularly-delivered antibiotics due to the severe tissue injury. Moreover, burn wounds leave the host immunocompromised with endogenously decreased levels of immunoglobulin gamma (IgG). Without treatment, burn wound infections can spread and develop into sepsis with the associated production of inflammatory cytokines, including interleukin-1 (IL-1), IL-6, and tumor necrosis factors (TNFs). Burn wound infections may also result in delayed healing, increased scarring, conversion of a partial thickness defect to a full thickness defect and increased nutritional demands.
Intravenous immunoglobulin (IVIG) has been used increasingly to treat both bacterial and viral infections and primary and secondary immunodeficiency disorders. WIG is comprised of pooled human polyclonal antibodies from normal donors which are used as a substitution therapy for primary and secondary antibody deficiencies and to treat immune-mediated diseases, including autoimmune and systemic inflammatory conditions. Immunoglobulins promote the opsonization and phagocytosis of bacteria, neutralization of bacterial toxins, inhibition of microbial attachment, and the complement-induced lysis of bacteria. See Felts et al. Burns 25:415-423 (1999).
Direct and local delivery of protective immunoglobulins to wound and burn sites represents a rational means to overcome the lack of vascularization of burn wounds as well as biofilm barriers. Local delivery of IgG, both prophylactically and post-infection, was demonstrated to improve survival in mouse models of Pseudomonas aeruginosa infected burn wounds. See Felts et al. Burns 25:415-423 (1999).
Advances in the bioengineering of prosthetic devices has improved the lives of millions of patients. However, this progress has been tempered by implant-associated infections that often resist antibiotic treatment. Infectious organisms, including Pseudomonas aeruginosa, preferentially target synthetic implanted materials, eliciting serious and costly infections that frequently require removal of the colonized device.
Initial microbial adhesion is a primary determinant of biomaterial colonization because initially adhering microorganisms often progress to a mature biofilm attached to the biomaterial surface. The focus of research aimed at reducing biofilm formation on prostheses has been directed toward modifying or coating the surface of the implanted materials. Approaches utilizing surface chemistry and antibiotic-releasing coatings, however, have not been fully successful.
Because surgical sites are often immunocompromised, a promising approach involves the immunostimulation of the local wound site. Studies have shown that pooled polyclonal human antibodies opsonize infecting bacteria, and pooled antibodies can inhibit Pseudomonas aeruginosa adhesion rates and surface-growth dynamics, thus reducing biofilm formation. See Poelstra et al. J. Biomed. Mat. Res. 51:224-232 (2000).
Peritonitis is often caused by ulcers, appendicitis, diverticulitis, ileus, gunshot or stab wounds, disturbances during abdominal surgery, and continuous ambulatory peritoneal dialysis (CAPD). Nosocomial peritonitis, caused by exogenous pathogenic bacteria including Pseudomonas aeruginosa, is an especially acute problem for immunocompromised and geriatric populations.
Current treatment regimens for peritonitis focus on antibiotics, however, antibiotic resistance occurs at a significant rate and is frequently associated with clinical failure. IVIG has shown promising but inconsistent results in peritonitis, however, as with burn wounds, local (peritoneal) delivery of pooled polyclonal immunoglobulin against Pseudomonas aeruginosa was shown to significantly reduce infection in a mouse model. See Barekzi et al. Antimicrob. Agents Chemotherap. 43:1609-1615 (1999).
Treating Pseudomonas aeruginosa infections with antibiotic regimens has become increasingly difficult because, inter alia, antibiotic resistant strains have arisen. The emergence of passive antibody therapy for the prevention and treatment of Pseudomonas aeruginosa infections, though promising, has been tempered by the availability purified human antibodies, free of non-human animal antibodies, that bind specifically to Pseudomonas aeruginosa in clinical quantities.
Non-human antibody preparations, including murine monoclonal antibodies, are not generally acceptable for human therapies because of their immunogenicity. Human polyclonal antibody preparations, although suitable for human therapies, have variable titers of protective antibodies for Pseudomonas aeruginosa and a high cost of purifying antibodies from multiple donors.
Monoclonal antibodies theoretically can be made in unlimited quantity, at a low cost and with a desired specificity. However, efficacious human monoclonal antibodies are difficult to make and require human B cells expressing appropriate antibodies to be transformed with Epstein-Ban virus. The resulting monoclonal antibody preparations would not likely be appropriate for human therapeutic use. Moreover, most of the human monoclonal antibodies tested to date have been IgM which penetrate poorly into pulmonary tissue and can be associated with immune complex formation and enhanced inflammation.
Therefore, there is a need for purified human IgG antibodies that bind specifically to Pseudomonas aeruginosa, methods for its preparation and use, and pharmaceutical compositions and kits thereof.